The present disclosure generally relates to precipitated particles having tailored properties and, more specifically, to wellbore circulation fluids containing such precipitated particles and methods for use thereof.
Treatment fluids can be used in a variety of subterranean treatment operations. Such treatment operations can include, without limitation, drilling operations, cementing operations, stimulation operations, production operations, remediation operations, sand control treatments, and the like. As used herein, the terms “treat,” “treatment,” “treating,” and grammatical equivalents thereof will refer to any subterranean operation that uses a fluid in conjunction with achieving a desired function and/or for a desired purpose. Use of these terms does not imply any particular action by the treatment fluid or a component thereof, unless otherwise specified herein. More specific examples of illustrative treatment operations can include, for example, drilling operations, primary cementing operations, secondary cementing operations, fracturing operations, gravel packing operations, acidizing operations, scale dissolution and removal operations, sand control operations, consolidation operations, and the like. Treatment fluids used in conjunction with a treatment operation may also be referred to equivalently herein as “wellbore circulation fluids.”
Wellbore circulation fluids frequently contain one or more types of particulate materials intended to assist the fluid in performing its intended function. Non-limiting functions of particulate materials within a wellbore circulation fluid may include, for example, densifying the fluid, propping fractures within the subterranean formation matrix, forming a filter cake to promote fluid loss control, and the like. When used for densification purposes, the particulate materials may be referred to as “weighting particles.”
Weighting particles are frequently incorporated within wellbore circulation fluids to provide densification, particularly when the wellbore circulation fluid's density needs to be increased beyond that possible with a brine carrier fluid alone or any other type of carrier fluid. Maintaining sufficient density can be critical in order to perform various types of subterranean treatment operations successfully. During drilling operations, for example, a wellbore circulation fluid's density must be high enough to exert sufficient pressure on the walls of the wellbore to prevent blowouts from occurring. However, the hydrostatic pressure may need to be limited in order to reduce the possibility of instigating damage within the surrounding subterranean formation matrix. In another non-limiting example, the density of a spacer fluid may need to be regulated to limit its mixing with other fluids introduced before or after the spacer fluid (e.g., a drilling fluid or a cementing fluid). The amount and native density of the weighting particles may collectively determine the ultimate density of the wellbore circulation fluid. The shape of the weighting particles, in turn, may influence their native density.
In addition to their densification function, weighting particles may similarly impact the rheological performance of a wellbore circulation fluid, including the sag, viscosity, and yield strength of the fluid, for example. As used herein, the term “sag” will refer to vertical inhomogeneity in the density of a wellbore circulation fluid due to particle settling. Sag can occur when a wellbore circulation fluid is static or being circulated and can result from the combination of secondary flow and gravitational forces, for example. If settling is prolonged, density of the wellbore circulation fluid in the upper part of the wellbore can decrease below acceptable levels and result in a loss of hydrostatic pressure. As with densification effects, the shape of weighting particles may similarly influence their ability to alter a fluid's rheological performance in a desired manner. The native particle shape of weighting particles may likewise affect their fluid loss control performance. Undesired rheological or fluid loss control performance can be problematic for a number of reasons, including potential failure of a subterranean treatment operation or instigation of formation matrix damage.
Conventional weighting particles often comprise various types of high-density commodity materials, such as ground minerals. Optionally, sieving or a similar technique may be conducted to limit a ground mineral to a chosen range of particle sizes. Ground barite, a mineral comprising predominantly barium sulfate, is a representative example of a conventional weighting particle. However, many other types of weighting particles prepared from ground minerals will be familiar to one having ordinary skill in the art and may be selected for a given application. For example, a particular type of weighting particle and an amount thereof may be chosen to be chemically compatible with the conditions present in a wellbore and to provide a desired degree of fluid densification, among other factors.
Grinding techniques are frequently limited in the breadth of particle shapes that can be produced from a mineral source. Not only are particle shapes limited, but the baseline physical and chemical properties of native mineral compositions themselves represent essentially fixed features with ground mineral particles. Accordingly, if a weighting particle formed from a ground mineral does not convey a desired set of properties to a wellbore circulation fluid, there may be few options available other than utilizing an entirely different type of weighting particle altogether, which may not be a viable solution in some circumstances. For example, cost, sub-optimal performance, and/or chemical incompatibilities may preclude the use of an alternative weighting particle type.
As a further difficulty, high-quality sources of barite and other native minerals are becoming less and less readily available at a reasonable cost. Lower-quality barite sources, for example, may contain inclusions that are not barium sulfate. These inclusions may undesirably alter the barite's properties, increase abrasiveness (e.g., quartz and related inclusions), and lower the barite's density compared to that obtained from higher-quality barite sources. As a result, ground barite weighting particles obtained from lower-quality sources may not perform as this material has historically under similar wellbore conditions and/or in like-formulated wellbore circulation fluids. Similar difficulties may be encountered with other types of ground-mineral weighting particles. Accordingly, conventional reliance on ground-mineral weighting agents can make a well operator's job exceedingly complex and provide limited opportunities for tailoring a wellbore circulation fluid to a given set of circumstances.